Spark-plug



A. M. FAIRCHILD.

SPARK PLUG.

APPLICATION FILEE MAY 2?. ma.

Patented Feb. 22, 1921.

UNITED s'rA'rss PATENT OFFICE.

ALICE HAUDE FAIBOHILD, O1! CHICAGO, ILLINOIS, ASSIGNOB TO CHARLES K. HARDING, OF CHICAGO, ILLINOIS.

SPARK-PLUG.

Specification of Letters Patent.

Patented Feb. 22. 1921.

Application filed Kay 27, 1918. Serlu 80. 236,983.

To allwhom it may concern: 4

Be it known that I, Amen MAUDE F AIR- omu), a citizen of the United States, and a resident of the city of Chicago, in the county of Cook and State of Illmois, have made certain new and useful Improvements in Spark-Plugs, of which the followlng specification is such a full, clear, and exact description as will enable others skilled in this art and the other arts to which this art most nearly appertains to make and use the same.

The accompanying drawings show a spark plug illustrative of the type of apparatus which forms the subject of my invention.

M invention relates generally to electrical ignition devices for internal combustion engines and more particularly to the detachable portion forming part of the wall of the inclosed space within which the ex plosion of the fuel mixture is produced by the discharge of a high tension current across the are formed between the terminals of a lurality of conducting electrodes.

This detachable portion 1 commonly called a spark plug usually carries two metallic terminals 2 and 3 with one of the conducting metallic electrodes extending entirely therethrough and a non-metallic insulating means 4 formi a portion of the wall and extending entirely therethrough from the inside to the outside of the combustion space. V.

Figure 1 is the vertical section view through this improved spark pin and Fig. 2 is'the vertical section iough'the insulator.

The conducting electrode extending through the plug as well as the conductin parts connecting with the opposlte terminal may be made of any suitable metallic substance as most of the metals now commonly used in spark plugs have suflicient mechanb a that zirconium end and zirconium silicate when constituting from 50 to 90% of the mass forms a ceramic structure having properties which produce an insulating non-metallic structure that has more suite 1e physical characteristics and desirable properties than any other of the ceramic materials such as. stoneware, china and'porcelain heretofore known or used in spark plugs.

Zirconia (ZrO zirconium oxid has been well known for man years having been used lar ely in incan escent, mantles of the earl elsbach type and their immediate pre ecessors. It was next largely used as a substitute for the lime structure in oxyhydrogen or calcium light and its fire resisting properties are well known.

The fact that zirconia formed an important constituent in the structure of the glower in the Nernst lamp might lead to the assumption that it would be unsuitable for use as a heat resistin insulating structure for spark plugs but have found by numerous tests within the last two years that it forms a more desirable constituent of a body for a spark plug insulator than any other of the numerous oxids of other compounds with which I have experimented and that it can be substituted with great improvement for china clay, feldspar, silica, magnesium silicate and other constituents heretofore em loyed in stoneware, china or porcelain insu ators.

Of the various processes for forming earthen ware structures those dependin on water shrinkage such as forming on a w eel or shaping in a plaster Paris mold or castlng a thin slip can not be employed where large quantities of zirconia is used on account of its lack of the pro erties characteristic of clay, that is, capi lary shrinkage into a hard compact mass but structures containing a large quantity of finely ground zirconium silicate such as the mineral zircon or finely ground baddeleyite a natural ore containing a high percentage of zirconium oxid with from 5 to 15% plastic clay can be readil formed into quite intricate shapes by w at is known as the dry formmg process frequently described as pressing a moist dust into steel molds.

A moist granulated zirconium mass con taining as ittle as 5% of clay and about 12% of water can be placed in a closely fitting steel die and s'ub ected to a pressure of from 5 to 8,000 pounds to the square inch and formed into a structure that will shrink which may be fired to any hi h temperature available without danger o undue fusing or shrinkage.

Havin now fully described my invention what I c aim is 1. A spark plu having metallic conducting electrodes an non-metallic wall forming and 'insulatin means consistin of a ceramic structure ormed from plastlc clay and zirconium com ounds.

2. A spark plug aving metallic conducting electrodes and non-metallic wall forming and insulating means comprising a ceramic structure consisting of zirconia compounds and a clay binder.

3. A spark plu having metallic conducting electrodes an non-metallic wall forming an insulating means consisting of a ceramic structure containing clay and zir conium compounds.

4. As a new article manufactured, an insulator for spark plugs comprising a ceramic structure of clay containing zirconia compounds in varKing proportions.

In testimony w ereof I have signed this s ecification at .Chica o, in the'county of 00k and State of IllIIlOiS, this 29 day of May, 1917.

ALICE MAUDE FAIRCHILD. 

